Eight crew members of a Chinese-owned cargo ship died after their vessel sank in rough seas off the South Korean harbour of Pohang, coastguard officials said Wednesday.

The Panamanian-registered 8,461-tonne freighter, carrying a 19-member crew, sank late Tuesday during a storm as it was waiting to enter Pohang and unload its cargo.

"Eight bodies have been recovered, eight others survived, and three are still missing," a South Korean coastguard spokesman told AFP.

China's state media reported that 18 of the 19 crew members were Chinese, including the captain who was among the dead.

The other crew member was Vietnamese, China's official news agency Xinhua said.

The ship, the CHENGLU15, was owned by China's Lishen International Shipping Group Corp., the agency said. (AFP)